Optimization of mid-IR photothermal imaging for tissue analysis

Infrared Spectroscopic Imaging Advances as an Analytical Technology for Biomedical Sciences

“…Since the detected signal imposes a limit on the spatial frequency collected in an imaging experiment, using a visible range wavelength to detect IR contrast is an excellent illustration using photothermal imaging. − In a typical embodiment, an IR source illuminates the sample, and if there is any vibrational energy levels matching with the incident frequency, IR light is absorbed causing a thermal expansion of the material as a result of relaxation. This expansion causes a refractive index change, which can be probed through the thermal lensing mechanism using a visible laser. − The contrast, thus, is based on IR absorption, but the detected signal and spatial resolution is determined by the characteristics of visible wavelengths.…”

Modeling the Thermoelastic Sample Response for Subdiffraction Infrared Spectroscopic Imaging

“…Subdiffraction IR imaging can also be achieved by reducing the wavelength of detected light to the visible regime to measure the consequence of absorption upon illumination with IR light, i.e., the sample’s thermal response to IR absorption-induced heating. Photothermal imaging − relies on the thermal-induced optical changes of the sample and can achieve optical resolution, which is subdiffraction compared to the exciting, IR light . This approach relies on more complex instruments and the signal generated depends on the thermal, optical, and elastic response of the material.…”